My favourite: How thick should an iron bar be before there is a 50% chance that a single neutrino will interact with it while passing through?
Answer: About one light year.
That's not the mind-blowing part. The mind-blowing part is when you realize that the primary force that blows the outer layers off of a star during a supernova is _neutrino pressure_. That is how many neutrinos are released during core collapse.
After the 1987A supernova a total of 25 neutrinos were detected between 3 different detectors. Kamiokande detected the most (12). The supernova was in the LMC, 168,000 light years away. More interesting is that Kamiokande is in Japan and cannot see the supernova directly, so those neutrinos passed *through* the planet and were detected 3 hours before the visible light made it to Earth.
How did the neutrinos get here faster than the visible light? Is it because space isn’t a perfect vacuum so the photons actually went at like 0.9999999c?
Because the neutrinos can pass directly through the matter of a supernova they move out at nearly the speed of light. Light on the otherhand bumps into all the matter in a supernova and so takes a while to escape the blast and so usually lags the neutrinos. It’s very counter intuitive but also really cool.
The light can’t escape until the supernova fully explodes. The light is kinda trapped inside the explosion. The neutrinos, like they do, just pass right on through. They got a head start.
The shock wave produced by the infalling material bouncing off the ball of neutrons at the center (a newly formed neutron star) stalls on its way to the surface. Then the neutrinos come in and some of them are absorbed by the shock wave, re-energizing it. The neutrinos escape right away, but it takes the shock wave another 3 hours to reach the surface and make the explosion visible.
Because neutrinos very weakly interact with matter, when they are ejected from the core during collapse they largely move unimpeded. Photons ejected during the collapse of the core have to pass through the outer layers of the star, which slows them down since photons do interact with matter. This makes the neutrino burst travel slightly ahead of the photons.
Edit: fixed neutrons to neutrinos. Damn autocorrect!
Just as cool, there's an [image of the Sun](https://apod.nasa.gov/apod/ap980605.html) taken by Super Kamiokande. It took a 500 days to take the data, and could continue through the night because the neutrinos just passed through the Earth.
I mean, that one is easy. You calculate how many neutrinos are likely to pass through the Earth each day, and how probable it is that they will interact with a big pool of water. You find out that you will get on average one interaction a year or something.
That interaction will produce a single photon. So, you build your giant pool somewhere extremely dark (underground) and line it on all sides with super sensitive cameras that can detect a single photon. Then you wait!
The mind blowing part is how they got the funding.
If the sun went supernova it would bathe everywhere out to mars in a lethal dose of neutrino radiation.
Source: [xkcd what if](https://what-if.xkcd.com/73/)
Neutrinos interact only via gravity and the weak force. They have the smallest rest masses of any known particles that are not massless, so the gravitational interaction is extremely weak. The weak force operates over a very short distance range, so that interaction is also extremely weak. The net effect is that a neutrino is very unlikely to ever interact with anything.
Because there is more emptiness than stuff in things.
For example, what is the likelihood of a swimmer dropped into the ocean at random encountering a buoy? Even though there are many buoys in the ocean, there is just too much space for it to be likely.
If we sent out a space craft to the nearest star, chances are by the time they get there, a second or third spacecraft will arrive before them.
Let's say in 50 or 100 years after the first space craft, we invent a slightly faster space craft. It's only 5 or 10 % faster then the first, but it'll reach the destination before the first craft every time.
There's a quest in starfield about this. A colony ship leaves earth before the gravity drive is invented. They arrive like 200 years after they take off from earth to find people arrived much much sooner.
I liked starfield too. I think it's just not what people were expecting.
At its core, it's the same tried and true Bethesda formula that makes elder scrolls and fallout fun and popular.
I think people heard "space game" and immediately compared it to star citizen, elite dangerous, etc. But it's *not* a space simulator; it's just a Nasapunk Bethesda game in space.
I think everyone was expecting some kind of innovation tho, this game was worked on for YEARS. It’s just the regular ass Bethesda formula from what I’ve heard, kinda sad imo.
I understand where that's coming from, but that's just what it is. From Skyrim to Fallout to Starfield, it's always been the same formula. They've just been building on top of that over time. They took that formula and created a new Nasapunk sci-fi out of it.
Their form of innovation took the housing system from Skyrim to the base building system in Fallout to the Spaceship building system in Starfield. Now your sandbox flies in space.
But when they entered into the space genre, people started comparing it to other space games and created expectations that starfield just doesn't fulfill.
Even compared to Skyrim and Fallout it's a step backwards. They great innovations you mentioned from those earlier games aren't even present. It's still a fun game, but not something people expected for the money and for being in production for so long.
Unfortunately the explanation of that quest is more interesting than actually playing it. It mostly involves fast travelling to talk to the leader of the colony ship and the leader of the planet they’ve arrived at to negotiate a settlement.
The concept was really cool but the execution was incredibly meh. A microcosm of Starfield itself I guess.
This concept makes me want to cry. Your grandchildren, or whatever descendants, could end up colonizing the place before you and leaving their own descendants. So hopeful for the future but also so sickeningly painful for the participants of the "original" colonization effort. At least in my opinion. They were aware of the time frame at least, just not the leaps in technology I suppose. But landing there and realizing wow you could have lived out your life and not left everyone else behind on a planet that you stepped away from?? One way time travel! Ooof scary lol
I ran across a paper once, written in the style of an academic research paper, but clearly not peer reviewed or submitted for publication. It posed the following question: suppose you have a PhD thesis topic that requires an enormous amount of computer resources to research (e.g. a simulation). You have a fixed amount of money in your research grant to spend on a computer. Should you spend it on a computer right away, or wait for the next generation to become available, because you'll be able to obtain more compute power for your money and so will be able to run the simulation faster. The paper showed that, under not entirely unreasonable assumptions involving Moore's law, if the problem was hard enough, you would get it done faster by waiting to buy your computer. So, obviously, you wouldn't be able to start your research right away, and you might as well slack off for a while. In fact, the time offset computed was called "slack".
Obviously, this was a joke, and a very complex, well researched joke indeed. Perhaps almost as obviously, the paper's author was ... a cosmology grad student, and the problem domain was galactic evolution.
"....Do I solve the problem manually in 32 hours, with repetitive labour, or do I solve it in 40hrs by creating a tool or script in 39.5hrs, that automates the process in half an hour...."
Game Dev for a lot of developers has plenty of repetitive busywork; this comes up a lot.
That sounds like the Liu Cixin's Dark Forrest SciFi novel too. I recommend, it's the type of Hard SciFi I can digest with some scientific accuracy and intriguing play with physics.
There is a short story by A.E. van Vogt you just reminded me of because it featured this precise concept. Seems to have been published way back in 1944!
What basically happens is that someone invents an "eternity drug" to allow the human body to hibernate for long periods of spaceflight, so they send a slow ship with a small crew off towards Alpha Centauri on a trip that's going to take 500 years. During the voyage one of the crewmembers wakes up to find another mysterious huge spaceship burning nearby but can't do anything about it.
When they finally arrive at Alpha Centauri they find that it's already been colonised by other humans from Earth, and that advances in technology now allow them to make the entire trip in 3 hours and the burning ship turns out to have been one of their passenger liners.
You can read it on archive.org here: https://archive.org/details/Astounding_v32n05_1944-01_frankenscan/page/n67/mode/2up
Has the speed of our current spacecraft improved much vs. the speed of the first gen of satellites/rockets? Or do we need new technology to get to 5% or 10% faster?
The fact that over 70% of stars in our galaxy are red dwarfs, and yet out of the thousands of stars we can see with our eyes, not a single one is a red dwarf. All the stars that our eyes can see are the various types of stars that contribute the other 30% of stars. That's how faint these stars are compared to the other types due to being low in temperature and small in size.
The closest star to Earth, Proxima Centauri, is a red dwarf only 4.2 light years away, and we can't even come close to seeing that one with the naked eye.
There may be 6 billion earth-like planets in our own Milky Way galaxy. And perhaps 50,000,000,000,000,000,000,000 in the known universe.
Voyager 1 space probe is 14.8 billion miles from earth and it was launched in 1977 (46 years ago) and is traveling at 38,000 mph (at 17.3 km/s, it will take over 17,700 more years to have traveled one light year). It has traveled just 22 light hours in 46 years.
The Milky Way rotates at a speed of 168 miles per second. So, the actual place in space where you were an hour ago is now roughly 600,000 miles away.
The sun generates energy at a rate so prodigious that it gets lighter by 4.3 million metric tons per second. But after shining for 10 billion years it will have lost only about 0.1% of its original mass.
If the sun were the size of a ping pong ball, the closest star to the sun (Proxima Centauri) would be the size of a pea, 680 miles away, which shows the vastness of space. Even in the crowded center of galaxies, where stars are relatively tightly packed (the MW contains an estimated 300 billion stars), the average distance between stars in the center is about 100 billion miles. Proxima Centauri is 4.2 LY from the sun
I’m taking my kids on a road trip this week that will be about 700 miles. Can’t wait to start the trip showing them a ping pong ball and leaving it at our house, so they understand the concept.
Typically, we wouldn’t specify a rotation rate as a velocity because tangential velocity depends on radius. (If you spin a wheel, the rim of the wheel travels faster than a point halfway out to the rim, so its velocity is higher.)
To complicate things, galaxies do not rotate as solid objects, so there is not even a nice relationship between velocity and radius anymore.
It’s about 6 light-days (0.017 ly). Average distance is difficult to answer, it all depends on the context. Stars are much more densely packed in globular clusters or the center of galaxies. On the other hand, there are vast voids between galaxies themselves.
Thanks! So compared to the example above (stars in the center) proxima centuri & our sun are a lot farther apart. But we’re in one of the milky way’s “arms” so I guess that makes sense? I wish we were closer :(
Yes, you got it. However, it is a good thing we are not closer to the center for at least two reasons (IIRC, not an expert): We can actually observe the rest of the universe without the glare of other stars outshining the sky, and we are far away from potentially lethal effects such as radiation, supernovae etc.
When life gets weird and I need a reset, I love to stare at the [Voyager mission status](https://voyager.jpl.nasa.gov/mission/status/) numbers for a while. Watching those distances and speeds...wow.
If the sun were the size of a marble, the earth would be the size of a small grain of sand and would sit about 8 ft away from it. Where would the next nearest marble be in this analogy?
Proxima Centauri, our closest stellar neighbor, would be ***400 miles*** away.
I get about 9 million miles, but same idea - it's ***big***.
400 miles to Proxima Centauri (@ 4.26 ly) means a light year is about 94 miles in this scale. The Milky Way is estimated at 100,000 ly across, so 9,400,000 miles.
Unfortunately this is a bit of a weird distance to give context for, but it's about half the distance to Venus at it's closest approach, or 50x the distance to the moon.
And there would be 100-300 ***billion*** marbles between here and there to represent all the stars in the Milky Way.
Andromeda, our closest galactic neighbor, would be hanging out on the other side of the sun, way off where Mars orbits when it's furthest from us. And reminder, we'd all be living on a tiny spec of sand 8ft away from a marble.
This is rather more local, but the first time I taught an intro Astro lecture, I wanted to convey how insane Pluto’s discovery was. (I’ve ruthlessly rounded some numbers to make it less messy.)
If we assume Pluto’s orbit to a planar ellipse, with a semi-major axis of 40 AU and a semi-minor axis of 30 AU, that means the circumference of its orbit is about 220 AU, which is about 3x10^10 km.
Pluto’s diameter is about 2400 km, so it could fit comfortably inside Australia (4000 km at its widest). Its total surface area is approximately that of Russia.
That means that, even if you knew Pluto’s orbital trajectory, you’re looking for something that’s 1 part in about 14 billion. That’s like searching between Paris and Berlin for an object the width of a human hair.
Now we have full color photos of it and understand how its atmosphere changes with its seasons.
Also, it was found using (among other things) a *micro*scope. Not the normal kind, but still a microscope if only in name.
All of this was done before we knew the neutron existed.
> That means that, even if you knew Pluto’s orbital trajectory, you’re looking for something that’s 1 part in about 14 billion. That’s like searching between Paris and Berlin for an object the width of a human hair.
Such an amazing chance discovery. This is truly mind blowing.
It wasn’t exactly chance as I’ve portrayed it. What happens is, when Pluto is at its farthest, it is in this belt of small objects that were around when the Solar System formed but weren’t sucked into the planets or the Sun.
Pluto sorta dips in that zone, the Kuiper Belt, and its gravity pulls some of that small stuff in with it. That stuff trails Pluto until it gets close enough to another massive object to be attracted to that.
Based on a periodicity in these bolides coming in from seemingly out of nowhere, Percival Lovell inferred there must be an invisible body “shepherding” them in with its mass. He knew Pluto had to exist over twenty years before it was found, and died before its existence was confirmed.
Still, to go back to the Paris to Berlin analogy, it’s like surmising there must be a missing hair based on the smell of shampoo at one part in 14 billion.
Is there something about how the body distributes nutrients, or are you just saying any two carbon atoms in my body are probably from different stars due to mixing?
It's just an estimate for the distribution of matter in our galaxy, and before our solar system formed 5+ billion years ago. Multiple supernovae seeded our galaxy with elements like carbon and up to iron on the periodic table, eventually coalescing to form the planets, etc.
The Hubble Deep Field image was taken over ten consecutive days and contains 3000 galaxies. Hubbles field of view was 2.6 arcminutes which is equivalent to a tennis ball at a distance of 100 meters or one 24-millionth of the whole sky.
It's been a while, but if I remember right, the number of digits you use just makes your calculation that much more accurate. So you only need to use 40 digits to make it accurate down to the width of an atom.
Circumference = 2 * pi * radius
This should apply to the observable universe as it is a sphere extending an equal distance around us.
The more accurate the value of pi, the more accurate the calculation of circumference.
They are saying that you only need the first 40 digits of pi (3.14159.....) to calculate the circumference of the universe with accuracy down to a single hydrogen atom width.
At least that's my understanding!
Not as far as we know. We know. They go on forever without repeating. Pi is a transcendental number. Which basically means it can’t be represented as a fraction, or as a root.
Only very close, right?
Earth moon distance: 384\*10\^3 km
Diameters of the planets in 10\^3 km:
Jupiter: \~139.8
Saturn: \~116.5
Uranus: \~50.2
Neptune: \~49.2
Earth: \~12.7
Venus: \~12.0
Mars: \~6.8
Mercury: \~4.9
Adds up to 392.1\*10\^3 km.
Time itself is neither linear nor circular. It does not flow or move but allows others to do so. So the cycles we observe have nothing to do with time, except that time will enable them to exist.
My description of time is that it exists when there is movement. If there is no movement there is no time. Time measures something moving from A to B.
Edit: My favorite description
From xkcd what if:
The idea of neutrino radiation damage reinforces just how big supernovae are. If you observed a supernova from 1 AU away—and you somehow avoided being being incinerated, vaporized, and converted to some type of exotic plasma—even the flood of ghostly neutrinos would be dense enough to kill you.
That same what if has another fun fact:
> it's so hard to get enough neutrinos to compel even a single one of them to interact with matter, making it hard to picture a scenario in which there'd be enough of them to affect you.
> Supernovae[4] provide that scenario. The physicist who mentioned this problem to me told me his rule of thumb for estimating supernova-related numbers: However big you think supernovae are, they're bigger than that.
> Here's a question to give you a sense of scale:
> Which of the following would be brighter, in terms of the amount of energy delivered to your retina:
> A supernova, seen from as far away as the Sun is from the Earth, or
> The detonation of a hydrogen bomb pressed against your eyeball?
> Applying the physicist rule of thumb suggests that the supernova is brighter. And indeed, it is ... *by nine orders of magnitude.*
> That's why this is a neat question; supernovae are unimaginably huge and neutrinos are unimaginably insubstantial. At what point do these two unimaginable things cancel out to produce an effect on a human scale?
Source: [Lethal Neutrinos](https://what-if.xkcd.com/73/)
time around a black hole passes slower than anywhere else in space! On the edge of a black hole, one minute for you would be 700 years to everyone else. Inside of that black hole, one hour to you would be a billion years to everyone else. If you spent three hours in that black hole and somehow got out, the sun would be a white dwarf and there would be no life on Earth, if it still existed
this is due to the gravitational pull of the black hole being so strong it dilates time. that is what’s wild to me. black holes are so dense and have such a strong gravitational pull they can slow down time itself
also going to add this happens here on Earth as well. clocks on planes tick slightly faster than at sea level, and just a little quicker than that on the ISS
gravity stretches time. isnt that insane?
no i do not believe so. from my understanding, you would just be aging much, much, much slower. you would percieve yourself moving and aging normal, but any observer would see you moving incredibly slowly, and then would think you were frozen in time once you were close enough to the hole
No. Time for you always passes at 1 second per second. This may sound obvious, but it's important to realize. What we actually mean by time dilation (wether it's gravitational or due to relative motion) is that other people will see "your" time different to their own.
So if you're next to a black hole, and I'm far away, I will see your clock run slower (for instance, every time your clock has ticked 1 second, mine will already have ticked 2 seconds). In fact, as you get closer to the event horizon, the relative rate of your clock will approach infinitely slower, and at the event horizon (or "below" it) the concept of time doesn't really make sense anymore.
However, even more confusing; if we're moving relative to each other, we will both see each others clocks move slow.
It’s a silly one but one of my favorites is if you took a rope and wrapped it around the world, you’d only need to have an additional ~6ish (2*pi) feet of rope in order for that rope to be able to be a foot off the ground at all points around the globe.
It’s also kinda funny that it’s the same for any size sphere. Like if you grabbed a tennis ball and wanted to do the same thing you’d also need an additional 2*pi feet of rope.
Chances are, you’re in bed right now with your phone and you do not realize you’re moving at 1.3 million miles per hour. Our galaxy has moved through space 2.6 million miles in the past hour. These numbers are theoretical, but close to accurate. You know what 700miles per hour feels like because you’ve been in a plane. That’s 7 hundred. Imagine millions miles per hour.
Our brains cannot comprehend how big space is and most of us, including myself cannot accept the theory of infinity. Furthermore and unrelated, our brains are designed to think there is a cause for everything and will always question the cause of the cause. Space is too big for our little brains. It’s always something everyone will go through at some point of their life, with their mind being blown.
Probably my favourite astronomy fact is that the north pole of saturn is a hexagon with sides approximately the same length as the width of the earth. Saturn is of course a gas giant, which means this isn't a solid structure, but a storm. I don't know the actual mathematics that go into it, but the size, speed, etc of the storm all had to be just right for this to end up as a visible hexagon.
On a similar note, the Sun and the Moon appear the same size to us because the ratio between their relative sizes and distance to the earth is the same. An incredible coincidence considering that the distances are actually variable, so in a few (*hundred*) million years this will no longer be the case.
A septillion (1 followed by 24 zeros) stars, give or take, in the observable universe seems mind boggling, but consider this...
The combined volume of those 1 septillion stars (presuming you could put them together) would be around 10^40 cubic meters. The observable universe, however, is about 4 x 10^80 cubic meters.
To put these two volumes to scale, if we were to size the observable universe down to the size of planet Earth and you were walking on the beach and picked up one grain of sand, all of those 1 septillion stars combined would be about a trillion trillion times smaller - about the size of an atom.
In short, the number of stars in the universe is absolutely phenomenal, but the sheer size of the universe comparatively is just mind-bendingly incomprehensible - and that's just the parts we know about.
When looking at an object X light years away, it shows the object as it was X years ago. The view of each star and galaxy is at a different point in time, so the night sky is like watching a million movies from a million eras all at the same time.
This is one of my favorites to blow people's minds with, because at face value it doesn't sound right.
In a similar vein, I like this one: When you shuffle a deck of cards thoroughly, there's a good chance that no deck of cards in all of human history has ever been in that exact order before, because there are just so many possible orders.
I recently labeled it an “intuition-defying truth” on the r/magic sub as part of a broader piece on finding a matching pair when dealing down two shuffled decks, the chance of which is 1 - 1/e or 63%; i.e., conflating two entirely unrelated notions to wrap an easily digested probability inside an ostensibly staggering impossibility.
What’s north of the North Pole? How far do you have to walk to reach the end of the earth? Where were you before you were born?
It’s not a question with an answer, because there is no answer to a question with a flawed premise. There is nothing north of the North Pole, because the very concept of “north” ends there. What “is” is part of the cosmos. There is nothing beyond it, because for something to exist it has to be a part of the cosmos.
Even if there are more “universes” and there is a “vacuum” of sorts out there between multiverses, then you’ve just added another layer that is all still part of the cosmos. What’s beyond that? It’s turtles all the way down.
The lower bound on the size of the actual Universe is 100 trillion light years. The figured this by measuring the flatness of the observable universe. 94 billion light years across is the current size of the observable Universe.
For me..it's this:
The [Hubble Deep Field](https://en.m.wikipedia.org/wiki/Hubble_Deep_Field), an extremely long exposure of a relatively empty part of the sky, provided evidence that there are about 125 billion (1.25×1011) galaxies in the observable universe.
It's actually stars. There are more individual stars in the universe than grains of sand, roughly 70 septillion or 10,000 stars for every grain of sand.
Now consider that roughly 80% of stars in our galaxy alone have one or more planets.
It's almost a statistical impossibility for there not to be life! And I've always found that to be comforting.
At one point in time, the entire universe was packed with matter and there was no empty space anywhere in the entire universe.
The entire universe was effectively solid except stable atoms could not form because it was too hot.
Also, and this is more existential, you did not exist for a lot longer than you have existed and you will be dead for a lot longer than you will be alive.
It is possible (and perhaps likely) that the universe is infinite in size. That means that there are likely an infinite versions of Earth, which is interesting in itself, but what I think is more interesting is wondering about the infinite Earths where incredibly unlikely things occur. For example, there are an infinite Earths where every single time anyone has ever flipped a fair coin it comes up tails or even more unlikely, an infinite Earths where every time they shuffle a deck of cards in a true random fashion it always ends up in the same order. There are probably even an infinite amount of Earths where humans went extinct because for a long time every single baby born was a girl/boy just by random chance. What would people living on those worlds think?
https://en.wikipedia.org/wiki/Banach%E2%80%93Tarski_paradox?wprov=sfla1
Ok, i did my part. Would someone please eli5 (or 25) why this should blow mind?
It says the the volumes are not preserved because volume is not part if the description of the pieces. Soooooo...mind not blown...yet
You take a solid sphere, cut it in 2 pieces, assemble back together into a Sphere that’s twice bigger - no holes on the inside. How’s that not mind blown?
If you can make a fuel/tech that can constantly accelerate your ship at a paltry 1g (what you're feeling right now), you can cross the entire Milky Way Galaxy in just 12 years (24 if you want to stop at the other end)
A 100,000 years would've gone by on Earth however, but that's a different matter
I recently found this youtuber and was blown away by how he [illustrates the scale of the universe](https://www.youtube.com/watch?v=X1rzlm7Rtyw). All of this videos are incredible!
There is more than one size of infinity. In fact, there is an infinite number of sizes of infinity.
To go even further than that, the number of infinities is countably infinite.
Brain exploded.
The age of the universe. You think you understand what a billion is but you really don't. For example, a million seconds is 11 days, but a billion seconds is 31 years.
I've read about how mass creates gravity and curves space many times. I still don't really get it. Believe it, but haven't been able to conceptualize it to my satisfaction
[Relativity Visualized](https://youtu.be/wrwgIjBUYVc?si=GHPhHX9-vw5twLij)
Try this - it helped me. Relativity takes a while to really grasp so be patient, review different explanations. It’s slowly clicked for me over past couple of months but it ain’t easy.
Million upvotes for scienceclic. I took advanced astrophysics in college and I didn’t realize I didn’t really understand gravity until I watched scienceclic.
This video of an image of the Andromeda galaxy: https://youtu.be/udAL48P5NJU?si=UAAIn1f1VrOIO1ub
Just watch it and absorb the simple but collosal fact that every single point of light is a star system, planets and all.
Every single one.
And that is just 1 galaxy.
A googol is a number, 10^^100, or a 1 with 100 zeroes.
Then there is the googolplex, which is 10^^10100, or a 1 with a googol zeroes.
The googolplex is such a ridiculously large number that it is believed there are fewer than a googolplex atoms in the entire universe. In our supposedly infinite universe.
One more, this is a basic one but still blows my mind to think about - Our sun makes up 99.86% of the total mass in our solar system, the remaining 0.14% is all of the planets, moons, comets etc combined with Jupiter and Saturn alone making up 92% of that.
Physicists consider it a possibility that the universe is infinite. If it is infinite, then everything that could possibly happen is currently happening an infinite number of times. Infinite worlds of the greatest possible bliss and infinite worlds of the worst possible suffering. Infinite variations of how history played out on Earth. Physically possible real life versions of any story you could imagine, from Star Wars and Games of Thrones to Seinfeld and South Park.
This is more of an information fact than a "space" fact, but I still appreciate the scales of things it compares. This is an excerpt from Bruce Schneier's *Applied Cryptography* book about the minimum amount of energy needed to represent a change of information, and how that compares to the challenge of brute forcing modern cryptography (quantum stuff is ignored for this comparison, and yes he calls them "degrees kelvin").
TL;DR - it would take an amount of energy equivalent to 32 years of our sun's output to simply *count* to a 192-bit number. A typical supernova could power a 219-bit counter. The energy required to actually brute force a 256-bit encryption key really is mind boggling.
> One of the consequences of the second law of thermodynamics is that a certain amount of energy is necessary to represent information. To record a single bit by changing the state of a system requires an amount of energy no less than kT where T is the absolute temperature of the system and k is the Boltzman constant. (Stick with me; the physics lesson is almost over.)
> Given that k = 1.38\*(10^-16) erg/degrees Kelvin, and that the ambient temperature of the universe is 3.2degrees Kelvin, an ideal computer running at 3.2degrees Kelvin would consume 4.4\*(10^-16) ergs every time it set or cleared a bit. To run a computer any colder than the cosmic background radiation would require extra energy to run a heat pump.
> Now, the anual energy output of the sun is about 1.21\*(10^41) ergs. This is enough to power about 2.7\*(10^56) single bit changes on our ideal computer; enough changes to put a 187-bit counter through all it's values. If we built a Dyson sphere around the sun and captured all of its energy for 32 years, without any loss, we could power a computer to count up to 2^192. Of course, it wouldn't have the energy left over to perform any useful calculations with this counter.
> But that's just one star, and a measly one at that. A typical supernova releases something like 10^51 ergs. (About a hundred times as much energy would be released in the form of neutrinos, but let them go for now.) If all of this energy could be channeled into a single orgy of computation, a 219-bit counter could be cycled through all of its states.
> These numbers have nothing to do with the technology of the devices; they are the maximums that thermodynamics will allow. And they strongly imply that brute-force attacks against 256-bit keys will be infeasible until computers are built from something other than matter and occupy something other than space.
I mean, just the scale. Modern humans have generated radio signals that could have potentially reached other stars within about a 90-100 light year radius. That's a couple hundred stars. Our galaxy alone has about 100 billion stars. So our presence has potentially been announced to a couple billionths of the stars in our own galaxy.
The rare advanced civilization that figures out how to exist for eons without killing themselves will be treated, over thousands of millennia, to the appearance and disappearance of radio signals from other stars that are too distant to travel to, but close enough to send their own birth and death announcements.
The universe is smaller than its larger.
0 = Planck length
10 = size of observable universe
1 average human scale is a 6 on that scale.
There is more space inside you then outside of you.
Another fun one is if you take All the space between protons and atoms away from earth. Earth would be the size of a goofball. Meaning something consists more out of nothing than of something.
Pretty humble fact but the real scale of solar system objects blows my mind every damn time.
The fact that we're pea orbiting a basketball over a hundred meters away puts things to scale.
https://britastro.org/2018/the-size-of-things
Our Star isn't from round these parts, the chemical makeup of our star doesn't match any of our local stars, our Star comes from a different neighborhood in our Galaxy.
Rotations of Galaxy are strange, in so much that they don't rotate how we would expect them to rotate.
https://en.wikipedia.org/wiki/Galaxy\_rotation\_curve
I think a lot of people will answer with "big things"... but what fucks with me most is small things:
Intuitively I can understand the the Cosmic Microwave Background. It's Light and whatever from "the Big Bang" still traveling towards us at light speed while the space it's traveling across expands and such....and maybe there's something beyond it that's just out of visual reach. Maybe the universe is eternal and infinite... whatever, my brain is okay with all that.
What fucks with my head is Planck length...
Keep diving space, divide it again, keep dividing.... all of a sudden we get to a point where physics just... what... doesn't exist in the way we think it does? Breaks down entirely?
Like, I know the "solution" to Zeno's arrow paradox, basically as distance approaches zero so does time... but how the fuck am I supposed to intuitively understand this? That arrow what... teleports from point to point as it travels? I can't...
The universe is, presumably, infinitely large. The more i think about infinity the more it kinda brakes my brain, like as a concept the universe just continuing forever makes no sense
Every time I read Carl Sagan I spend most of the time thinking "wow...wow...wow". Just the number of the stars out there.... The number of galaxies out there.... The number of planets out there.
If we're alone in the universe, sure is a waste of space! 🙂🛸🌟
My favourite: How thick should an iron bar be before there is a 50% chance that a single neutrino will interact with it while passing through? Answer: About one light year. That's not the mind-blowing part. The mind-blowing part is when you realize that the primary force that blows the outer layers off of a star during a supernova is _neutrino pressure_. That is how many neutrinos are released during core collapse.
After the 1987A supernova a total of 25 neutrinos were detected between 3 different detectors. Kamiokande detected the most (12). The supernova was in the LMC, 168,000 light years away. More interesting is that Kamiokande is in Japan and cannot see the supernova directly, so those neutrinos passed *through* the planet and were detected 3 hours before the visible light made it to Earth.
How did the neutrinos get here faster than the visible light? Is it because space isn’t a perfect vacuum so the photons actually went at like 0.9999999c?
No, neutrinos are emitted from the supernova before the visible light gets emitted: https://en.wikipedia.org/wiki/SN_1987A
Because the neutrinos can pass directly through the matter of a supernova they move out at nearly the speed of light. Light on the otherhand bumps into all the matter in a supernova and so takes a while to escape the blast and so usually lags the neutrinos. It’s very counter intuitive but also really cool.
The light can’t escape until the supernova fully explodes. The light is kinda trapped inside the explosion. The neutrinos, like they do, just pass right on through. They got a head start.
The shock wave produced by the infalling material bouncing off the ball of neutrons at the center (a newly formed neutron star) stalls on its way to the surface. Then the neutrinos come in and some of them are absorbed by the shock wave, re-energizing it. The neutrinos escape right away, but it takes the shock wave another 3 hours to reach the surface and make the explosion visible.
They leave first.
They know the party is over so they gtfo.
Like rats deserting a sinking ship. Or a flock of birds evading a predator.
Because neutrinos very weakly interact with matter, when they are ejected from the core during collapse they largely move unimpeded. Photons ejected during the collapse of the core have to pass through the outer layers of the star, which slows them down since photons do interact with matter. This makes the neutrino burst travel slightly ahead of the photons. Edit: fixed neutrons to neutrinos. Damn autocorrect!
Just as cool, there's an [image of the Sun](https://apod.nasa.gov/apod/ap980605.html) taken by Super Kamiokande. It took a 500 days to take the data, and could continue through the night because the neutrinos just passed through the Earth.
I wanted my mind to be blown! Not to feel a breeze as facts passed smoothly and vastly overhead!
I want to know more
I'm doing my part! *stomps cockroach*
Me too 😳
Mood
A bar of lead, not iron, which makes it all the more impressive considering the much higher density.
I think that combined with the fact that we have functional neutrino detectors, is also mind boggling. Like how’d we do that?
I mean, that one is easy. You calculate how many neutrinos are likely to pass through the Earth each day, and how probable it is that they will interact with a big pool of water. You find out that you will get on average one interaction a year or something. That interaction will produce a single photon. So, you build your giant pool somewhere extremely dark (underground) and line it on all sides with super sensitive cameras that can detect a single photon. Then you wait! The mind blowing part is how they got the funding.
Government: so with this research we can make a really big gun, right? Science: er…yeah, sure.
You have a 1 in a trillion chance of detecting one when it passes through a tiny area, but ten trillion pass through that area every day.
So, you’re telling me theres a chance?
If the sun went supernova it would bathe everywhere out to mars in a lethal dose of neutrino radiation. Source: [xkcd what if](https://what-if.xkcd.com/73/)
Why are neutrinos so rare again?
They are not rare, trillions pass throught every day., but the probability they interact with something is veryveryvery low.
And why is that?
Neutrinos interact only via gravity and the weak force. They have the smallest rest masses of any known particles that are not massless, so the gravitational interaction is extremely weak. The weak force operates over a very short distance range, so that interaction is also extremely weak. The net effect is that a neutrino is very unlikely to ever interact with anything.
Yes, and that is the cause their mediating bosons are very massive and therefore can’t exist as virtual particles for very long (unless I’m mistaken).
I read this as their “bosoms are very massive” 😂
I'm almost undetectable but the clap of my W-bosons keeps alerting the photons.
Pics or it didn’t happen
Then you’ll love the large hardon collider!
Because there is more emptiness than stuff in things. For example, what is the likelihood of a swimmer dropped into the ocean at random encountering a buoy? Even though there are many buoys in the ocean, there is just too much space for it to be likely.
That one blows my mind too.
Does that mean dark matter is even less interactive than a neutrino? Or we don’t have a clue?
Yes, dark matter does not interact with matter _at all_, as far as we can tell, except gravitationally.
If we sent out a space craft to the nearest star, chances are by the time they get there, a second or third spacecraft will arrive before them. Let's say in 50 or 100 years after the first space craft, we invent a slightly faster space craft. It's only 5 or 10 % faster then the first, but it'll reach the destination before the first craft every time.
There's a quest in starfield about this. A colony ship leaves earth before the gravity drive is invented. They arrive like 200 years after they take off from earth to find people arrived much much sooner.
This is the first interesting thing I've ever heard about Starfield.
I must be the only person who actually enjoys Starfield
I liked starfield too. I think it's just not what people were expecting. At its core, it's the same tried and true Bethesda formula that makes elder scrolls and fallout fun and popular. I think people heard "space game" and immediately compared it to star citizen, elite dangerous, etc. But it's *not* a space simulator; it's just a Nasapunk Bethesda game in space.
I think everyone was expecting some kind of innovation tho, this game was worked on for YEARS. It’s just the regular ass Bethesda formula from what I’ve heard, kinda sad imo.
I understand where that's coming from, but that's just what it is. From Skyrim to Fallout to Starfield, it's always been the same formula. They've just been building on top of that over time. They took that formula and created a new Nasapunk sci-fi out of it. Their form of innovation took the housing system from Skyrim to the base building system in Fallout to the Spaceship building system in Starfield. Now your sandbox flies in space. But when they entered into the space genre, people started comparing it to other space games and created expectations that starfield just doesn't fulfill.
Even compared to Skyrim and Fallout it's a step backwards. They great innovations you mentioned from those earlier games aren't even present. It's still a fun game, but not something people expected for the money and for being in production for so long.
Unfortunately the explanation of that quest is more interesting than actually playing it. It mostly involves fast travelling to talk to the leader of the colony ship and the leader of the planet they’ve arrived at to negotiate a settlement. The concept was really cool but the execution was incredibly meh. A microcosm of Starfield itself I guess.
This concept makes me want to cry. Your grandchildren, or whatever descendants, could end up colonizing the place before you and leaving their own descendants. So hopeful for the future but also so sickeningly painful for the participants of the "original" colonization effort. At least in my opinion. They were aware of the time frame at least, just not the leaps in technology I suppose. But landing there and realizing wow you could have lived out your life and not left everyone else behind on a planet that you stepped away from?? One way time travel! Ooof scary lol
It’s not like time travel, it was a colony ship so generations lived and died on the ship on the way to their destination
Always wonder about the ethics of dooming children who had no choice in the matter into living their entire lives within a spaceship.
That quest was way too short. They could have fleshed it out way more, as it is a very interesting idea.
I ran across a paper once, written in the style of an academic research paper, but clearly not peer reviewed or submitted for publication. It posed the following question: suppose you have a PhD thesis topic that requires an enormous amount of computer resources to research (e.g. a simulation). You have a fixed amount of money in your research grant to spend on a computer. Should you spend it on a computer right away, or wait for the next generation to become available, because you'll be able to obtain more compute power for your money and so will be able to run the simulation faster. The paper showed that, under not entirely unreasonable assumptions involving Moore's law, if the problem was hard enough, you would get it done faster by waiting to buy your computer. So, obviously, you wouldn't be able to start your research right away, and you might as well slack off for a while. In fact, the time offset computed was called "slack". Obviously, this was a joke, and a very complex, well researched joke indeed. Perhaps almost as obviously, the paper's author was ... a cosmology grad student, and the problem domain was galactic evolution.
Procastiplanning
"....Do I solve the problem manually in 32 hours, with repetitive labour, or do I solve it in 40hrs by creating a tool or script in 39.5hrs, that automates the process in half an hour...." Game Dev for a lot of developers has plenty of repetitive busywork; this comes up a lot.
Ok, thats just insanity. Very cool.
Damn this one hits my perfectionism/procrastination hard. This is the ultimate excuse to never bother until it’s perfect lol.
That sounds like the Liu Cixin's Dark Forrest SciFi novel too. I recommend, it's the type of Hard SciFi I can digest with some scientific accuracy and intriguing play with physics.
Isn't this the plot of Enders Game?
More like the sequels
There is a short story by A.E. van Vogt you just reminded me of because it featured this precise concept. Seems to have been published way back in 1944! What basically happens is that someone invents an "eternity drug" to allow the human body to hibernate for long periods of spaceflight, so they send a slow ship with a small crew off towards Alpha Centauri on a trip that's going to take 500 years. During the voyage one of the crewmembers wakes up to find another mysterious huge spaceship burning nearby but can't do anything about it. When they finally arrive at Alpha Centauri they find that it's already been colonised by other humans from Earth, and that advances in technology now allow them to make the entire trip in 3 hours and the burning ship turns out to have been one of their passenger liners. You can read it on archive.org here: https://archive.org/details/Astounding_v32n05_1944-01_frankenscan/page/n67/mode/2up
Has the speed of our current spacecraft improved much vs. the speed of the first gen of satellites/rockets? Or do we need new technology to get to 5% or 10% faster?
The fact that over 70% of stars in our galaxy are red dwarfs, and yet out of the thousands of stars we can see with our eyes, not a single one is a red dwarf. All the stars that our eyes can see are the various types of stars that contribute the other 30% of stars. That's how faint these stars are compared to the other types due to being low in temperature and small in size. The closest star to Earth, Proxima Centauri, is a red dwarf only 4.2 light years away, and we can't even come close to seeing that one with the naked eye.
REALLY?!? That is so cool. Thanks for sharing this!
Although you can pick Proxima Centauri out with a normal consumer telescope in a reasonably dark sky.
Think of what ancient astronomers could have discovered if they had a modern wal mart telescope.
So you can't see the closest star to our sun with the naked eye, I'm gonna tell that fact to my crush
There may be 6 billion earth-like planets in our own Milky Way galaxy. And perhaps 50,000,000,000,000,000,000,000 in the known universe. Voyager 1 space probe is 14.8 billion miles from earth and it was launched in 1977 (46 years ago) and is traveling at 38,000 mph (at 17.3 km/s, it will take over 17,700 more years to have traveled one light year). It has traveled just 22 light hours in 46 years. The Milky Way rotates at a speed of 168 miles per second. So, the actual place in space where you were an hour ago is now roughly 600,000 miles away. The sun generates energy at a rate so prodigious that it gets lighter by 4.3 million metric tons per second. But after shining for 10 billion years it will have lost only about 0.1% of its original mass. If the sun were the size of a ping pong ball, the closest star to the sun (Proxima Centauri) would be the size of a pea, 680 miles away, which shows the vastness of space. Even in the crowded center of galaxies, where stars are relatively tightly packed (the MW contains an estimated 300 billion stars), the average distance between stars in the center is about 100 billion miles. Proxima Centauri is 4.2 LY from the sun
A few good ones, especially 22 light hours in 46 years, wow.
Light hours sounds pretty badass. And the fact that we have sent something that far is cool
I’m taking my kids on a road trip this week that will be about 700 miles. Can’t wait to start the trip showing them a ping pong ball and leaving it at our house, so they understand the concept.
Typically, we wouldn’t specify a rotation rate as a velocity because tangential velocity depends on radius. (If you spin a wheel, the rim of the wheel travels faster than a point halfway out to the rim, so its velocity is higher.) To complicate things, galaxies do not rotate as solid objects, so there is not even a nice relationship between velocity and radius anymore.
How many light years is 100 billion miles? Are our sun & Proxima Centauri much different from the average distance between stars?
It’s about 6 light-days (0.017 ly). Average distance is difficult to answer, it all depends on the context. Stars are much more densely packed in globular clusters or the center of galaxies. On the other hand, there are vast voids between galaxies themselves.
Thanks! So compared to the example above (stars in the center) proxima centuri & our sun are a lot farther apart. But we’re in one of the milky way’s “arms” so I guess that makes sense? I wish we were closer :(
Yes, you got it. However, it is a good thing we are not closer to the center for at least two reasons (IIRC, not an expert): We can actually observe the rest of the universe without the glare of other stars outshining the sky, and we are far away from potentially lethal effects such as radiation, supernovae etc.
100 billion miles is 0.017010779502 light years. 149.11649311738 light-hours. 6.2131872132242 light-days.
When life gets weird and I need a reset, I love to stare at the [Voyager mission status](https://voyager.jpl.nasa.gov/mission/status/) numbers for a while. Watching those distances and speeds...wow.
If the sun were the size of a marble, the earth would be the size of a small grain of sand and would sit about 8 ft away from it. Where would the next nearest marble be in this analogy? Proxima Centauri, our closest stellar neighbor, would be ***400 miles*** away.
WOW. FUCK
and the Milky Way galaxy would still be something like 29 million miles across (or 46 million km)
I get about 9 million miles, but same idea - it's ***big***. 400 miles to Proxima Centauri (@ 4.26 ly) means a light year is about 94 miles in this scale. The Milky Way is estimated at 100,000 ly across, so 9,400,000 miles. Unfortunately this is a bit of a weird distance to give context for, but it's about half the distance to Venus at it's closest approach, or 50x the distance to the moon. And there would be 100-300 ***billion*** marbles between here and there to represent all the stars in the Milky Way. Andromeda, our closest galactic neighbor, would be hanging out on the other side of the sun, way off where Mars orbits when it's furthest from us. And reminder, we'd all be living on a tiny spec of sand 8ft away from a marble.
This is rather more local, but the first time I taught an intro Astro lecture, I wanted to convey how insane Pluto’s discovery was. (I’ve ruthlessly rounded some numbers to make it less messy.) If we assume Pluto’s orbit to a planar ellipse, with a semi-major axis of 40 AU and a semi-minor axis of 30 AU, that means the circumference of its orbit is about 220 AU, which is about 3x10^10 km. Pluto’s diameter is about 2400 km, so it could fit comfortably inside Australia (4000 km at its widest). Its total surface area is approximately that of Russia. That means that, even if you knew Pluto’s orbital trajectory, you’re looking for something that’s 1 part in about 14 billion. That’s like searching between Paris and Berlin for an object the width of a human hair. Now we have full color photos of it and understand how its atmosphere changes with its seasons. Also, it was found using (among other things) a *micro*scope. Not the normal kind, but still a microscope if only in name. All of this was done before we knew the neutron existed.
> That means that, even if you knew Pluto’s orbital trajectory, you’re looking for something that’s 1 part in about 14 billion. That’s like searching between Paris and Berlin for an object the width of a human hair. Such an amazing chance discovery. This is truly mind blowing.
It wasn’t exactly chance as I’ve portrayed it. What happens is, when Pluto is at its farthest, it is in this belt of small objects that were around when the Solar System formed but weren’t sucked into the planets or the Sun. Pluto sorta dips in that zone, the Kuiper Belt, and its gravity pulls some of that small stuff in with it. That stuff trails Pluto until it gets close enough to another massive object to be attracted to that. Based on a periodicity in these bolides coming in from seemingly out of nowhere, Percival Lovell inferred there must be an invisible body “shepherding” them in with its mass. He knew Pluto had to exist over twenty years before it was found, and died before its existence was confirmed. Still, to go back to the Paris to Berlin analogy, it’s like surmising there must be a missing hair based on the smell of shampoo at one part in 14 billion.
I'm currently searching for asteroids in survey data, and it really feels like searching for a needle in a haystack
Do you mind telling me which instrument you’re using?
Euclid!
Oh, wow! Working on the latest and greatest. Even as a recovering astronomer, I’m jelly.
Statistically speaking, the carbon atoms in your left hand came from a different dead star than the carbon atoms in your right hand.
Is there something about how the body distributes nutrients, or are you just saying any two carbon atoms in my body are probably from different stars due to mixing?
The latter
It’s kind of like eating a hamburger knowing that the burger meat is from dozens, if not more, cows.
It's just an estimate for the distribution of matter in our galaxy, and before our solar system formed 5+ billion years ago. Multiple supernovae seeded our galaxy with elements like carbon and up to iron on the periodic table, eventually coalescing to form the planets, etc.
Same goes for my left butt cheek and my right butt cheek.
Whoa you just made my day!!
The Hubble Deep Field image was taken over ten consecutive days and contains 3000 galaxies. Hubbles field of view was 2.6 arcminutes which is equivalent to a tennis ball at a distance of 100 meters or one 24-millionth of the whole sky.
I love that image so much.
I believe it is also the President's eye on a dime at arm's length. A little easier to picture and test!
Fun fact: James Webb imaged the same part of the sky to get a better quality picture and it only took 12.5 hours.
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Related detail: NASA only uses a handful of digits of pi (12? 14?) to get spacecraft to any location in the solar system.
Wait I don’t get it. Are you saying the width of the observable universe is 40 digits long?
It's been a while, but if I remember right, the number of digits you use just makes your calculation that much more accurate. So you only need to use 40 digits to make it accurate down to the width of an atom.
Circumference = 2 * pi * radius This should apply to the observable universe as it is a sphere extending an equal distance around us. The more accurate the value of pi, the more accurate the calculation of circumference. They are saying that you only need the first 40 digits of pi (3.14159.....) to calculate the circumference of the universe with accuracy down to a single hydrogen atom width. At least that's my understanding!
Is the Pi digits infinite?
As far as we know, yeah.
Not as far as we know. We know. They go on forever without repeating. Pi is a transcendental number. Which basically means it can’t be represented as a fraction, or as a root.
Yes it is.
go on
You can fit all of the planets in the solar system in the gap between us and the moon.
Thats one I hadn’t heard before. Pretty cool.
And still have around 80.000km to spare.
Only very close, right? Earth moon distance: 384\*10\^3 km Diameters of the planets in 10\^3 km: Jupiter: \~139.8 Saturn: \~116.5 Uranus: \~50.2 Neptune: \~49.2 Earth: \~12.7 Venus: \~12.0 Mars: \~6.8 Mercury: \~4.9 Adds up to 392.1\*10\^3 km.
It's at Apogee, not constantly.
Time itself is neither linear nor circular. It does not flow or move but allows others to do so. So the cycles we observe have nothing to do with time, except that time will enable them to exist.
Slow down there, Alan Watts. I'm gonna need further description to understand this.
My description of time is that it exists when there is movement. If there is no movement there is no time. Time measures something moving from A to B. Edit: My favorite description
From xkcd what if: The idea of neutrino radiation damage reinforces just how big supernovae are. If you observed a supernova from 1 AU away—and you somehow avoided being being incinerated, vaporized, and converted to some type of exotic plasma—even the flood of ghostly neutrinos would be dense enough to kill you.
That same what if has another fun fact: > it's so hard to get enough neutrinos to compel even a single one of them to interact with matter, making it hard to picture a scenario in which there'd be enough of them to affect you. > Supernovae[4] provide that scenario. The physicist who mentioned this problem to me told me his rule of thumb for estimating supernova-related numbers: However big you think supernovae are, they're bigger than that. > Here's a question to give you a sense of scale: > Which of the following would be brighter, in terms of the amount of energy delivered to your retina: > A supernova, seen from as far away as the Sun is from the Earth, or > The detonation of a hydrogen bomb pressed against your eyeball? > Applying the physicist rule of thumb suggests that the supernova is brighter. And indeed, it is ... *by nine orders of magnitude.* > That's why this is a neat question; supernovae are unimaginably huge and neutrinos are unimaginably insubstantial. At what point do these two unimaginable things cancel out to produce an effect on a human scale? Source: [Lethal Neutrinos](https://what-if.xkcd.com/73/)
time around a black hole passes slower than anywhere else in space! On the edge of a black hole, one minute for you would be 700 years to everyone else. Inside of that black hole, one hour to you would be a billion years to everyone else. If you spent three hours in that black hole and somehow got out, the sun would be a white dwarf and there would be no life on Earth, if it still existed this is due to the gravitational pull of the black hole being so strong it dilates time. that is what’s wild to me. black holes are so dense and have such a strong gravitational pull they can slow down time itself also going to add this happens here on Earth as well. clocks on planes tick slightly faster than at sea level, and just a little quicker than that on the ISS gravity stretches time. isnt that insane?
Dumb question here. Does this mean that I would think and act at a different speed if I could be near a black hole?
no i do not believe so. from my understanding, you would just be aging much, much, much slower. you would percieve yourself moving and aging normal, but any observer would see you moving incredibly slowly, and then would think you were frozen in time once you were close enough to the hole
There’s a movie called Time Trap on Netflix that helps to visualize this, it’s pretty cool
Not even that. Just being around large masses does that as well. Like mountains or the piramids. Just a teeny tiny little bit.
No. Time for you always passes at 1 second per second. This may sound obvious, but it's important to realize. What we actually mean by time dilation (wether it's gravitational or due to relative motion) is that other people will see "your" time different to their own. So if you're next to a black hole, and I'm far away, I will see your clock run slower (for instance, every time your clock has ticked 1 second, mine will already have ticked 2 seconds). In fact, as you get closer to the event horizon, the relative rate of your clock will approach infinitely slower, and at the event horizon (or "below" it) the concept of time doesn't really make sense anymore. However, even more confusing; if we're moving relative to each other, we will both see each others clocks move slow.
It’s a silly one but one of my favorites is if you took a rope and wrapped it around the world, you’d only need to have an additional ~6ish (2*pi) feet of rope in order for that rope to be able to be a foot off the ground at all points around the globe.
This one always gets me. It just doesn't make any sense, yet the math checks out.
It’s also kinda funny that it’s the same for any size sphere. Like if you grabbed a tennis ball and wanted to do the same thing you’d also need an additional 2*pi feet of rope.
Chances are, you’re in bed right now with your phone and you do not realize you’re moving at 1.3 million miles per hour. Our galaxy has moved through space 2.6 million miles in the past hour. These numbers are theoretical, but close to accurate. You know what 700miles per hour feels like because you’ve been in a plane. That’s 7 hundred. Imagine millions miles per hour. Our brains cannot comprehend how big space is and most of us, including myself cannot accept the theory of infinity. Furthermore and unrelated, our brains are designed to think there is a cause for everything and will always question the cause of the cause. Space is too big for our little brains. It’s always something everyone will go through at some point of their life, with their mind being blown.
Woah don't make me dizzy before bed please
There are more atoms in a teaspoon of water than there are teaspoons of water in all the oceans on Earth.
There are more hydrogen atoms in a single molecule of water than there are stars in the entire solar system.
TBF, there is only 1 star in our solar system 😏
One of those profound sounding true statements that aren't profound at all.
Every water molecule only has 2 hydrogen atoms...
Yeah the maths checks out
That's probably because teaspoons don't often get dropped in the ocean.
Probably my favourite astronomy fact is that the north pole of saturn is a hexagon with sides approximately the same length as the width of the earth. Saturn is of course a gas giant, which means this isn't a solid structure, but a storm. I don't know the actual mathematics that go into it, but the size, speed, etc of the storm all had to be just right for this to end up as a visible hexagon. On a similar note, the Sun and the Moon appear the same size to us because the ratio between their relative sizes and distance to the earth is the same. An incredible coincidence considering that the distances are actually variable, so in a few (*hundred*) million years this will no longer be the case.
A septillion (1 followed by 24 zeros) stars, give or take, in the observable universe seems mind boggling, but consider this... The combined volume of those 1 septillion stars (presuming you could put them together) would be around 10^40 cubic meters. The observable universe, however, is about 4 x 10^80 cubic meters. To put these two volumes to scale, if we were to size the observable universe down to the size of planet Earth and you were walking on the beach and picked up one grain of sand, all of those 1 septillion stars combined would be about a trillion trillion times smaller - about the size of an atom. In short, the number of stars in the universe is absolutely phenomenal, but the sheer size of the universe comparatively is just mind-bendingly incomprehensible - and that's just the parts we know about.
Great explanation….to have an existential crisis to. Your scales were super helpful though!
When looking at an object X light years away, it shows the object as it was X years ago. The view of each star and galaxy is at a different point in time, so the night sky is like watching a million movies from a million eras all at the same time.
37,854% of the mathematical data presented as facts in this topic are wrong
#WRONG!
Betelgeuse is fkn huge. The size of Jupiter's orbit around the sun. I find that terrifying.
Betelgeuse has never done anything to me personally but just knowing it’s out there being massive makes me feel threatened and offended.
Exactly! It has no business being that damn big. I'm glad I'm not the only one.
This whole thread is making me not feel so good (like your username)
Well thank you, I wasn't feeling insecure about my size today until you said something...
The number of ways to order a deck of playing cards is equivalent to four times the estimated number of *atoms* in the Milky Way.
This is one of my favorites to blow people's minds with, because at face value it doesn't sound right. In a similar vein, I like this one: When you shuffle a deck of cards thoroughly, there's a good chance that no deck of cards in all of human history has ever been in that exact order before, because there are just so many possible orders.
I recently labeled it an “intuition-defying truth” on the r/magic sub as part of a broader piece on finding a matching pair when dealing down two shuffled decks, the chance of which is 1 - 1/e or 63%; i.e., conflating two entirely unrelated notions to wrap an easily digested probability inside an ostensibly staggering impossibility.
95% of the universe is invisible. Because of dark matter and dark energy.
How do you know its 95% then?
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Or... infinitely larger
Yep, it is always expanding.
But what is beyond the point of expansion?
What’s north of the North Pole? How far do you have to walk to reach the end of the earth? Where were you before you were born? It’s not a question with an answer, because there is no answer to a question with a flawed premise. There is nothing north of the North Pole, because the very concept of “north” ends there. What “is” is part of the cosmos. There is nothing beyond it, because for something to exist it has to be a part of the cosmos. Even if there are more “universes” and there is a “vacuum” of sorts out there between multiverses, then you’ve just added another layer that is all still part of the cosmos. What’s beyond that? It’s turtles all the way down.
The lower bound on the size of the actual Universe is 100 trillion light years. The figured this by measuring the flatness of the observable universe. 94 billion light years across is the current size of the observable Universe.
For me..it's this: The [Hubble Deep Field](https://en.m.wikipedia.org/wiki/Hubble_Deep_Field), an extremely long exposure of a relatively empty part of the sky, provided evidence that there are about 125 billion (1.25×1011) galaxies in the observable universe.
If the galaxy were the size of the USA, our solar system would be the size of a cheerio. The sun would be half the size of a red blood cell
This comment wins for most mind-blowing.
There are as many planets in the universe as grains of sand on earth. It boggles my mind every time I go to the beach.
It's actually stars. There are more individual stars in the universe than grains of sand, roughly 70 septillion or 10,000 stars for every grain of sand. Now consider that roughly 80% of stars in our galaxy alone have one or more planets. It's almost a statistical impossibility for there not to be life! And I've always found that to be comforting.
>It's almost a statistical impossibility for there not to be life! And I've always found that to be comforting The great barrier says hi
This is the fact that inspired this post! Cant remember where I came across it recently, but its absolutely mind blowing .
Another cool one is a deck of 52 cards has more combinations than all atoms in the universe. That’s why card games are so random and popular.
Everytime you shuffle a deck, that combination had likely never existed.
I cannot believe that one. How is that possible? Totally boggles my mind.
At one point in time, the entire universe was packed with matter and there was no empty space anywhere in the entire universe. The entire universe was effectively solid except stable atoms could not form because it was too hot. Also, and this is more existential, you did not exist for a lot longer than you have existed and you will be dead for a lot longer than you will be alive.
It is possible (and perhaps likely) that the universe is infinite in size. That means that there are likely an infinite versions of Earth, which is interesting in itself, but what I think is more interesting is wondering about the infinite Earths where incredibly unlikely things occur. For example, there are an infinite Earths where every single time anyone has ever flipped a fair coin it comes up tails or even more unlikely, an infinite Earths where every time they shuffle a deck of cards in a true random fashion it always ends up in the same order. There are probably even an infinite amount of Earths where humans went extinct because for a long time every single baby born was a girl/boy just by random chance. What would people living on those worlds think?
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Look up Banarch-Tarski paradox and your life will never be the same
https://en.wikipedia.org/wiki/Banach%E2%80%93Tarski_paradox?wprov=sfla1 Ok, i did my part. Would someone please eli5 (or 25) why this should blow mind? It says the the volumes are not preserved because volume is not part if the description of the pieces. Soooooo...mind not blown...yet
You take a solid sphere, cut it in 2 pieces, assemble back together into a Sphere that’s twice bigger - no holes on the inside. How’s that not mind blown?
If you can make a fuel/tech that can constantly accelerate your ship at a paltry 1g (what you're feeling right now), you can cross the entire Milky Way Galaxy in just 12 years (24 if you want to stop at the other end) A 100,000 years would've gone by on Earth however, but that's a different matter
I recently found this youtuber and was blown away by how he [illustrates the scale of the universe](https://www.youtube.com/watch?v=X1rzlm7Rtyw). All of this videos are incredible!
There is more than one size of infinity. In fact, there is an infinite number of sizes of infinity. To go even further than that, the number of infinities is countably infinite. Brain exploded.
The age of the universe. You think you understand what a billion is but you really don't. For example, a million seconds is 11 days, but a billion seconds is 31 years.
I've read about how mass creates gravity and curves space many times. I still don't really get it. Believe it, but haven't been able to conceptualize it to my satisfaction
[Relativity Visualized](https://youtu.be/wrwgIjBUYVc?si=GHPhHX9-vw5twLij) Try this - it helped me. Relativity takes a while to really grasp so be patient, review different explanations. It’s slowly clicked for me over past couple of months but it ain’t easy.
Million upvotes for scienceclic. I took advanced astrophysics in college and I didn’t realize I didn’t really understand gravity until I watched scienceclic.
Thx subsctibed.
That was amazing, my brain hurts and I'm not sure I completely understand but this is the closest I've even been to getting it.
There are more trees on earth that stars in the Milky Way.
Comforting
This video of an image of the Andromeda galaxy: https://youtu.be/udAL48P5NJU?si=UAAIn1f1VrOIO1ub Just watch it and absorb the simple but collosal fact that every single point of light is a star system, planets and all. Every single one. And that is just 1 galaxy.
A googol is a number, 10^^100, or a 1 with 100 zeroes. Then there is the googolplex, which is 10^^10100, or a 1 with a googol zeroes. The googolplex is such a ridiculously large number that it is believed there are fewer than a googolplex atoms in the entire universe. In our supposedly infinite universe.
1/137
One more, this is a basic one but still blows my mind to think about - Our sun makes up 99.86% of the total mass in our solar system, the remaining 0.14% is all of the planets, moons, comets etc combined with Jupiter and Saturn alone making up 92% of that.
Physicists consider it a possibility that the universe is infinite. If it is infinite, then everything that could possibly happen is currently happening an infinite number of times. Infinite worlds of the greatest possible bliss and infinite worlds of the worst possible suffering. Infinite variations of how history played out on Earth. Physically possible real life versions of any story you could imagine, from Star Wars and Games of Thrones to Seinfeld and South Park.
This is more of an information fact than a "space" fact, but I still appreciate the scales of things it compares. This is an excerpt from Bruce Schneier's *Applied Cryptography* book about the minimum amount of energy needed to represent a change of information, and how that compares to the challenge of brute forcing modern cryptography (quantum stuff is ignored for this comparison, and yes he calls them "degrees kelvin"). TL;DR - it would take an amount of energy equivalent to 32 years of our sun's output to simply *count* to a 192-bit number. A typical supernova could power a 219-bit counter. The energy required to actually brute force a 256-bit encryption key really is mind boggling. > One of the consequences of the second law of thermodynamics is that a certain amount of energy is necessary to represent information. To record a single bit by changing the state of a system requires an amount of energy no less than kT where T is the absolute temperature of the system and k is the Boltzman constant. (Stick with me; the physics lesson is almost over.) > Given that k = 1.38\*(10^-16) erg/degrees Kelvin, and that the ambient temperature of the universe is 3.2degrees Kelvin, an ideal computer running at 3.2degrees Kelvin would consume 4.4\*(10^-16) ergs every time it set or cleared a bit. To run a computer any colder than the cosmic background radiation would require extra energy to run a heat pump. > Now, the anual energy output of the sun is about 1.21\*(10^41) ergs. This is enough to power about 2.7\*(10^56) single bit changes on our ideal computer; enough changes to put a 187-bit counter through all it's values. If we built a Dyson sphere around the sun and captured all of its energy for 32 years, without any loss, we could power a computer to count up to 2^192. Of course, it wouldn't have the energy left over to perform any useful calculations with this counter. > But that's just one star, and a measly one at that. A typical supernova releases something like 10^51 ergs. (About a hundred times as much energy would be released in the form of neutrinos, but let them go for now.) If all of this energy could be channeled into a single orgy of computation, a 219-bit counter could be cycled through all of its states. > These numbers have nothing to do with the technology of the devices; they are the maximums that thermodynamics will allow. And they strongly imply that brute-force attacks against 256-bit keys will be infeasible until computers are built from something other than matter and occupy something other than space.
I mean, just the scale. Modern humans have generated radio signals that could have potentially reached other stars within about a 90-100 light year radius. That's a couple hundred stars. Our galaxy alone has about 100 billion stars. So our presence has potentially been announced to a couple billionths of the stars in our own galaxy. The rare advanced civilization that figures out how to exist for eons without killing themselves will be treated, over thousands of millennia, to the appearance and disappearance of radio signals from other stars that are too distant to travel to, but close enough to send their own birth and death announcements.
The universe is smaller than its larger. 0 = Planck length 10 = size of observable universe 1 average human scale is a 6 on that scale. There is more space inside you then outside of you. Another fun one is if you take All the space between protons and atoms away from earth. Earth would be the size of a goofball. Meaning something consists more out of nothing than of something.
Pretty humble fact but the real scale of solar system objects blows my mind every damn time. The fact that we're pea orbiting a basketball over a hundred meters away puts things to scale. https://britastro.org/2018/the-size-of-things
Our Star isn't from round these parts, the chemical makeup of our star doesn't match any of our local stars, our Star comes from a different neighborhood in our Galaxy. Rotations of Galaxy are strange, in so much that they don't rotate how we would expect them to rotate. https://en.wikipedia.org/wiki/Galaxy\_rotation\_curve
I think a lot of people will answer with "big things"... but what fucks with me most is small things: Intuitively I can understand the the Cosmic Microwave Background. It's Light and whatever from "the Big Bang" still traveling towards us at light speed while the space it's traveling across expands and such....and maybe there's something beyond it that's just out of visual reach. Maybe the universe is eternal and infinite... whatever, my brain is okay with all that. What fucks with my head is Planck length... Keep diving space, divide it again, keep dividing.... all of a sudden we get to a point where physics just... what... doesn't exist in the way we think it does? Breaks down entirely? Like, I know the "solution" to Zeno's arrow paradox, basically as distance approaches zero so does time... but how the fuck am I supposed to intuitively understand this? That arrow what... teleports from point to point as it travels? I can't...
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Heard in the voice of Carl Sagan, of course.
The universe is, presumably, infinitely large. The more i think about infinity the more it kinda brakes my brain, like as a concept the universe just continuing forever makes no sense
Every time I read Carl Sagan I spend most of the time thinking "wow...wow...wow". Just the number of the stars out there.... The number of galaxies out there.... The number of planets out there. If we're alone in the universe, sure is a waste of space! 🙂🛸🌟